In math, # usually denotes the number of elements in a set (cardinality).

For example, in this equation

enter image description here

the #D{x} operator denotes the number of elements in the set D that satisfies property x.

I am trying to render this character in TeX, and this code


gives this symbol:

enter image description here

What am I missing?


1 Answer 1


It seems the font used in the image is Adobe Times/URW Nimbus as provided by the txfonts package (or some very similar variant of it):


\[ \hat\thetaup_{ijk} = \hat P(X_i=x_{ij}\mid Y=y_k)
    = \frac{\#D\{X_i=x_{ij} \wedge Y=y_k\}}{\#D\{Y=y_k\}} \]

enter image description here

Original answer

The font used in your image is not the default Computer Modern font. You could use \text{\ttfamily\#}, which is closer to the symbol in the image, but still not the same:



$\#D$ vs. $\tthash D$

enter image description here

Wikipedia also just lists the standard \# as a symbol for cardinality.

For the exact same output, you need to find the font that provides this special hash character glyph.

  • 1
    txfonts has many weaknesses, avoid it and prefer newtxtext,newtxmath.
    – egreg
    Nov 12, 2019 at 8:38

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